Simple Interest Question

[creative8401]

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Hi everyone. Hope you are all having a nice holiday weekend. I'm having a little trouble with this simple interest question, and its coming from crack math program. They repeat the same style of question. At first I thought it was wrong, but they would have posted it on their site, IDK

A sum of money is invested at simple interest doubles in 5 years. In how many years will his investment be five times the initial sum of money.

Answer:
Let sum of money be "x"
X = x * r * 5
r = 0.2

4x = x * 0.2 * y
y = 20

What I'm confused on is that they take 5 years and put a "4x". Shouldnt it be "5x"?

thanks.

 

[baedero1]

the answer is ture.

because,

x + (x*0.2*y) = 5x

therefore, x*0.2*y = 4x

 

[PooyaH]

Hi everyone. Hope you are all having a nice holiday weekend. I'm having a little trouble with this simple interest question, and its coming from crack math program. They repeat the same style of question. At first I thought it was wrong, but they would have posted it on their site, IDK

A sum of money is invested at simple interest doubles in 5 years. In how many years will his investment be five times the initial sum of money.

Answer:
Let sum of money be "x"
X = x * r * 5
r = 0.2

4x = x * 0.2 * y
y = 20

What I'm confused on is that they take 5 years and put a "4x". Shouldnt it be "5x"?

thanks.

You can just do this one in your head! Just pick a number Like 2!!!
after the first 5 years you'd have 4, 10 years 6, 15 years 8, and 20 years 10 and 2 x 5 = 10! lol